Renewable doctor blade



y 7, 1966 M. G. WHITFIELD 3,251,339

RENEWABLE DOCTOR BLADE Filed Oct. 11, 1965 INVENTOR.

United States Patent.

3,251,339 RENEWABLE DOCTOR BLADE Marshall G. Whitfield, Brookfield, Conn. Whitfield Lab. Inc., P.0. Box 293, Bethe], Conn.)

Filed Oct. 11, 1965, Ser. No. 500,468

7. Claims. (Cl. 118122) This application is a continuation in part of my copending application Serial No. 216,177 filed August 10, 1962, now abandoned, and entitled Coating of Metal With Other Metals.

This invention relates to the coating of metal pieces with other metals, and more particularly to the coating of sheets, strips, ribbons, wires and the like of metal such as steel and iron, with highly oxidizable metals such as aluminum, magnesium, etc.

In the past the coating of sheets, strips, ribbons, wiresv and the like as above referred to has been carried out by passing the metal pieces or work to be coated through a bath of molten, coating or donor metal. However, it has been found to be very diflicult to obtain coatings of thedesired thickness and uniformity by this procedure. With a bath of highly oxidizable metal in the molten state, a film of oxide of a relatively tenacious nature forms on the surface of the bath. It is believed that this film tends to be drawn ontothe surface of the metal piece which is being coated as the latter leaves the bath, and that the oxide film ruptures periodically due to the drag placed on it as it is pulled across the surface of the bath. This results in the undesirable deposit of fragments of the film on the pieces being coated. Each time the adhering oxide film ruptures, it slides down the surface of the emerging metal Work and wipes off some of the desired coating metal. Thus there are produced successive transverse areas on the coated piece, having different thickness of coating, also, portions of the coating will include fragments of the oxide film, with the netresult that the coating metal film on the piece varies greatly in thickness and consistency.

The above disadvantages of this prior process and apsheets, strips, ribbons, wires or the like with highly oxi-- dizable metal such as aluminum, magnesium, etc. wherein the work is passed through a bath of the molten coating 'rnetal, characterized by a mechanical wiping of the work at the place of emergence of the latter, the apparatus comprising one or more flexible wiper or doctor members engaging either one or opposite sides of thework, preferably directly at the surface of the molten coating metal.

The wiper members are preferably strip-like in form, and constituted of molybdenum or another metal of the long series of Groups 4 to 6 or Group 8 of the Periodic System, such as tungsten, cobalt, and tantalum, or of an alloy of one or more of these metals. Also, the wiper "ice members may be provided with oxide protection or cermets coatings or the equivalent.

The engaging end portions of the wiper members may curve upwardly at the place where they engage the emerging coated strip, or they may curve downwardly into the surface portions of the bath. The wiper members are constructed to prevent any oxide skin on the surface of the molten metal from being drawn onto the surface of the emerging metal strip, sheet or ribbon, or at least large fragments-of oxide, and to prevent such skin from effecting an intermittent wiping action of the layer of coating adhering to the work. Thus, the wiper members facilitate the production of a uniform and consistent metallic coating on the metal pieces constituting the work.

The wiper members may be part of coils carried by suitable wheels or spindles which may be rotated from time to time to unwind additional material and make up for the gradual oxidation and consequent disintegration of the ends of the wiper members which engage the emerging work.

Another object of the present invention is to provide an improved apparatus in accordance with the foregoing, which is simple to construct.

A further object of the invention is to provide an improved apparatus for coating metal pieces With a donor metal as above set forth, which is efi'ective and reliable in its operation, eliminating to the maximum possible extent oxide-fragments and other impurities from the coating which has been applied to the work.

A feature of the invention resides in the provision of an improved apparatus as above characterized, which may be readily incorporated and applied to existing equipment, without involving appreciable change or expense.

Other features and advantages will hereinafter appear.

In the drawings accompanying this specification, similar'characters of reference are used to designate like components throughout the several views, in which:

FIG. 1 is a diagrammatic representation of an improved metal coating apparatus as provided by the invention, the showing being in the nature of a vertical sectional view.

FIG. 2 is a diagrammatic representation similar generally to that of FIG. 1, illustrating a modified form of apparatus of the invention.

FIG. 3 is a diagrammatic representation of another embodiment of the invention, such representation being in the form of a horizontal section through an emerging wire at the place of emergence.

FIG. 4 is a vertical section, taken on the line 44 of FIG. 3.

Considering first FIG. 1, there is shown a coating tank 10 having a bath 12 of molten metal, said bath being heated by any suitable heating device such as the immersion heater 14. The top surface of the bath 12 I of molten metal is indicated by the numeral 16.

For the purpose of coating a metal strip, sheet or the like, indicated at 18, the sheet is brought into the bath and led out again by suitable conveyor means, illustrated Patented May 17, 1966 and prevent their adhesion to the strip during the coating procedure. The wiper strips 26 and 28 are preferably formed of molybdenum or another'metal of the long series of Groups 4 to 6 or Group 8 of the Periodic System, which includes tungsten, cobalt and tantalum, or else are formed of an alloy of one or more of these metals. Also, the strips may be of a metal which is protected from the effects of heat and abrasion by oxide or cermets (ceramic containing material) coatings or the equivalent. As shown in FIG. 1, the wiper strips 26 and 28 are flexible and curved upward at the ends where engagement occurs between them and the emerging metal sheet which is to be coated. Also, the wiper strips 26 and 28 are in accordance with the invention, part of supply coils 34, 36 carried on spindles 37 as shown, by which the strips may be replenished or advanced as the engaging edges become worn, oxidized or disintegrated.

The curved end portions of the wiper strips 26, 23 are indicated at 39, 32 respectively. The curvature here may follow the natural meniscus of the molten metal, formed by the emerging strip 18.

Guide means for the wiper strips 26, 28 are provided in the form of roller-shoe pairs 38, 40, the rollers 38 being adapted to effect the advance of the strips 39, 32 when desired. For this purpose, the rollers 38 may be provided with teeth 39 receivable in suitable feed openings in the wiper strips.

In PEG. 1 the doctor or wiper members 26, 28 lie virtually on the surface of the bath, and the curved engaging ends may follow the upper curvature of such surfaces as effected by the surface tension and engagement with the emerging strip, sheet or ribbon.

Another embodiment of the invention is illustrated in FIG. 2, wherein the tank 100 has a bath 12a of molten metal having a top surface indicated by the broken line 16a. A heater 14a raises the temperature of the bath to the desired value. The strip 18a is guided through the bath 12a by conveyor rollers 20a, 22a as shown.

In accordance with the invention, doctor or wiper members or strips 26a, 28a supplied from turnable feed coils or rolls engage the emerging sheet 18a at the point or place of emergence 24a, such wiper strips having their engaging end portions curved downward as indicated at 30a, 32a. The wiper strips 26a, 28a are part of the supply rolls or coils 34a, 35a, and are guided by pairs of rollers and shoes 38a, 40a in a manner similar to that already described in connection with FIG. 1. The rollers 380 preferably are provided with teeth (not shown) engageable or receivable in matching feed openings in the wiper strips, to effect a positive advance of the same as needed during the disintegration or attrition of the engaging ends of the strips.

It will now be understood that, in accordance with the invention,.the provision of the coiled, renewable wiper strips 26, 28 (or 26a, 28a) located substantially at the surface of the bath 12 (or 120) prevents the deposit of oxide skin fragments on the emerging strip to the extent that a uniform, homogeneous coating is had. It is believed that the wiper strips effectively prevent the oxide skin from effecting an intermittent wiping action on the coated surface of the metal strips 18 or 18a, whereby there is facilitated the production of the aforesaid uniform and consistent coating. The wiper members function in this manner because of their intimate contact with the skin on the surface of the molten metal, which prevents such skin from being drawn onto the surface of the emerging metal strip or sheet.

In FIG. 2 the portions of the wiper members 26a, 28a other than the ends are shown as being disposed above the top surface 16a of the bath 12, such wiper members extending angularly downward toward the emerging strip 18a to engage the latter and also the oxide skin of the bath substantially at the place of emergence 24a of the strip. However, this different organization does not alter the effectiveness of the wiping action, and has the advanta e that the supply portions of the strips are not subject to the action of the oxide film.

Still another embodiment of the invention is illustrated in FIGS. 3 and 4. This embodiment involves the coating of work comprising elongate strips in the form of round wire. As shown, the work in the form of a round wire 18b is emerging from a bath 1212 of molten metal. Three wiper members 26b, 28b and 2911 coming from supply rolls (not shown) are mounted so that they con tact, and may be fed toward, the wire 18b along three directions which are related by 120 angles. At their forward portions adjacent the wire 18]) the wiper members 26b, 28b and 2% pass through and are positioned by stationary guide fittings 50, 52 and 54 respectively. At these forward or adjoining ends the wiper members 26b, 28b and 29b have arcuate edge portions which are bent upward and which engage the emerging wire 1811 along a total are which may be equal to 360.

By such organization a complete and continuous wiping action is had on the wire as it leaves the bath of molten metal. The wiper members 26b, 28b and 291) are advanced to replenish the end portion as these wear away from contact with the wire, as in the previous embodiments. The feeding of the wiper members or strips may be accomplished in any suitable manner, as for example like that explained above in connection with FIGS. 1 and 2.

As with the previous embodiments, the organization I illustrated in FIGS. 3 and 4 results in a uniform coating which is essentially free from oxide and other impurities that would otherwise be deposited on the wire 18b.

The apparatus involving the coiled wiper strips as described is seen to be essentially of simple construction, involving relatively few components whereby it may be easily serviced and maintained. The operation is effective and reliable in enabling a uniform coating free of oxide or other impurities to be obtained on metal pieces which are coated in a bath.

Variations and modifications may be made within the scope'of the claims, and portions of the improvement may be used without others.

I claim:

1. An apparatus for uniformly coating an elongate metallic member comprising, in combination:

(a) a tank for holding a bath of molten metal,

(b) conveying means for passing the elongate metallic member through said tank, into and out of the said bath to be coated thereby,

(c) a coil of strip material, a transverse edge of the free end of said coil engaging and wiping the metallic member at the place of emergence thereof from the bath, to prevent the deposit of film from the surface of the bath onto the member whereby the coating of the member is rendered uniform, and

((1) means supporting the coil to enable the same to be unwound for feeding the strip material toward the metallic member as the material is consumed by the wiping,

(6) means for feeding the strip material from the coil toward the metallic member,

(f) said feed means comprising a roller engaged with said strip material.

2. The invention as in claim 1, wherein:

(a) projections are provided on said roller, engageable with the strip material to feed the same.

3. The invention as in claim 1, wherein:

(a) a second coil of strip material is provided, a transverse edge of the free end of said second coil engaging and wiping another side of the metallic member at a point adjacent the engagement of the metallic member by the first-mentioned strip material, and

(b) means supporting the second coil to enable the same to be unwound to compensate for its attrition.

4. The invention as in claim 3, wherein:

(a) the metallic member comprises a wire of circular cross section.

5. The invention as in claim 3, wherein:

(a) the metallic member comprises sheet material.

6. The invention as in claim 3, wherein:

(a) the two ends of said strip material .are curved and flexed in the direction of travel of the metallic membet.

7. The invention as in claim 3, wherein:

(a) the two ends of said strip material are curved and flexed oppositely to the direction of travel of the metallic member.

Bleiber 118-125 X Bennett 15236 Lit et a1. 118-125 Harris et a1. l18-419 Smith et a1. 118-413 10 MORRIS KAPLAN, Primary Examiner. 

1. AN APPARATUS FOR UNIFORMLY COATING AN ELONGATE METALLIC MEMBER COMPRISING, IN COMBINATION: (A) A TANK FOR HOLDING A BATH OF MOLTEN METAL, (B) CONVEYING MEANS FOR PASSING THE ELONGATE METALLIC MEMBER THROUGH SAID TANK, INTO AND OUT OF THE SAID BATH TO BE COATED THEREBY, (C) A COIL OF STRIP MATERIAL, A TRANSVERSE EDGE OF THE FREE END OF SAID COIL ENGAGING AND WIPING THE METALLIC MEMBER AT THE PLACE OF EMERGENCE THEREOF FROM THE BATH, TO PREVENT THE DEPOSIT OF FILM FROM THE SURFACE OF THE BATH ONTO THE MEMBER WHEREBY THE COATING OF THE MEMBER IS RENDERED UNFORM, AND 